Darnell confirmed he would step down from his post as prexy of alternative entertainment at Fox when his contract is up next month. Darnell and Fox positioned the departure as his decision, but his departure comes on the heels of “American Idol” falling to record lows and a mixed track record for the network in unscripted programming of late. On Thursday, Fox’s most recent competition reality skein, “Does Someone Have to Go?,” bowed to a weak 1.3 rating/4 share in the adults 18-49 demographic in the 9 p.m. slot behind “Hell’s Kitchen.”

Nonetheless, Darnell has been a pillar of the network for nearly 20 yeas, and his departure promoted a comment from the big boss, News Corp. chairman-CEO Rupert Murdoch.

“Mike took risks at a critical time and was a pioneering force in shaping the reality programming genre that exists today,” Murdoch said. “He’s a smart and fearless executive who will be missed.”

Darnell has a well-earned reputation as one of the most colorful personalities in the network biz. A former child actor, the exec is known for sporting wide-brim cowboy hats and fringy shirts. As a programmer, he’s been a trailblazer who helped fuel the boom in unscripted programming with everything from “Cops” to tabloidy clip shows (“World’s Scariest Police Chases,” “When Animals Attack”) to the competition boom dominated for years by “American Idol.”

“I’ve been in ‘Reality’ since before it was even called that, and it has truly been an amazing ride,” he said. “However, the world has changed drastically over the last few years and now with hundreds of channels and limitless ways to watch television, I’ve decided this was the perfect time to take advantage of the rapidly changing marketplace.”

Darnell said he would take his time in determining his next move. Among the advisers he’s leaning on is WME reality chief Mark Itkin. He said there are “a lot of options on the table” and emphasized that he’s “not even close to making a decision.”

Darnell joined Fox in 1994 as director of specials after working for eight years at Fox’s Los Angeles O&O KTTV and the Fox Television Stations Group. Among the properties he supervised at the News Corp. broadcast outlet were “Idol,” of course, but also “The X Factor,” “So You Think You Can Dance,” and the trio of cooking-themed reality programs featuring Gordon Ramsay: “Masterchef,” “Hell’s Kitchen” and “Kitchen Nightmares.” Also under his aegis: “Are You Smarter Than A Fifth Grader.”

Among his other achievements at Fox was bringing young animator Seth MacFarlane into the fold. “Family Guy” was developed through Darnell’s division as an alternative series project in 1998.

Darnell also gave birth to some programming firestorms. The 2000 program “Who Wants To Marry A Multi-Millionaire, ” sparked outrage among select advocacy groups when it was revealed the “multi-millionaire” at the center of the show, which married him off to the winner, had a restraining order filed against him for domestic abuse. The 2001 series “Temptation Island” asked couples potentially to engage in sexual activity outside of an already established romantic relationship. A 2003 episode of reality show “Married By America” sparked an indecency fine (and long-running legal fight) with the FCC over an episode with a heavy dose of sexual content.

Darnell’s shows were often ratings-grabbers, but ad-sales executives at Fox often bemoaned early reality specials such as “When Animals Attack,” because they often made sponsors nervous.